Inhalers are used to deliver drugs into a patient's lungs. Typically, an inhaler contains or provides a mixture of drug particles and air or propellant gas. The mixture is delivered via the patient inhaling from a mouthpiece on the inhaler with the air or propellant gas carrying the drug particles into the patient's lungs.
In dry powder inhalers, the drug particles, in the form of a fine dry powder, are entrained into an airflow, and inhaled by the patient, for treatment for various conditions, for example, bronchial asthma. Drugs delivered via a dry powder inhaler can be used to treat many conditions, including those unrelated to lung conditions, via the systemic absorption of the drug into the bloodstream, via the lung.
For effective dose delivery using a dry powder inhaler, the powder particles must first be dispersed to form a powder/air aerosol. Various techniques for forming powder aerosols have been proposed. Some of these techniques use the airflow from the patient's inspiration alone to disperse the powder. Other techniques involve forming a powder aerosol by spinning a propeller within a chamber; generating a fast moving flow of air over or through the powder; and shaking, vibrating, or impacting a powder laden string, tape, or mesh, using mechanical devices or ultrasonics. In addition, various other techniques for generating powder aerosols have been proposed or used, with varying degrees of success. Challenges remain in achieving a dry powder inhaler which can effectively create a dry powder aerosol for inhalation, while also having advantages in other areas, such as effectiveness in creating an aerosol, reliability, complexity of design, costs, ergonomics, dose consistency, and other factors.
Dry powder inhalers have certain advantages over metered dose inhalers and nebulizers or liquid droplet inhalers. Typically, dry powder inhalers do not require propellant gases, which may be damaging to the environment. Dry powder inhalers generally also do not require a high level of user coordination between releasing a dose and inhaling the dose. As they do not release a burst or high speed plume of drug particles, having the release of the dose occur near simultaneously with inhalation is not required. Dry powder inhalers can also have relatively reliable and inexpensive designs.
Various techniques have been proposed for storing doses of powder in a dry powder inhaler. These techniques include bulk storage of the powder in a reservoir having a metering out device, gelatin capsules which are pierced or cut open, or blister disks having individual blisters which are punctured or sheared open. To better seal the pharmaceutical powder from the environment (to reduce caking, contamination, or other undesirable changes), individually sealed dose containers such as blister disks, are preferred. Inhalers using blister disks have had different ways of advancing the blister disk to deliver sequential doses, of opening the blisters, and of moving the powder out of the open blister for inhalation by the user. While test results on some of these types of inhalers have been promising, engineering challenges remain in providing reliable and accurate blister disk operations in a dry powder inhaler, while also providing advantageous human factors features.
Accordingly, it is an object of the invention to provide an improved dry powder inhaler.